I've created a multiboot USB drive using this guide: http://www.pendrivelinux.com/boot-multiple-iso-from-usb-via-grub2-using-linux/
I've put Linux Mint, Ubuntu, and now I'd like to also add Windows 8. Apparently there are some problems related to the way Windows 8 boots, using UEFI... I can't completely understand this. Is there a way to copy the Windows 8 ISO to the USB drive and just add an entry in the grub config?